1. Field of the Invention
The present invention relates to a compound spear sling, and more particularly to a compound spear sling having a pair of rotating pulley members each provided with a cam portion and a draw cable track for achieving a mechanical advantage.
2. Description of Related Art
The modern spear sling is a progressive version of its medevil counterpart and is an improvement over known non-triggered underwater spear fishing devices including pole spears, and Hawaiian slings.
Pole spears are spear fishing devices which include long poles which act as a spear. The elastic attached to the pole must be looped over the wrist which grips the pole. The pole is pushed backward after which the pole is gripped at a cocked position. The pole spear is released by loosening a grip on the pole. These pole spears are non-triggering and useful at close range only and are awkward due to excessive pole lengths.
The Hawaiian sling spear fishing device is a cylinder typically made of wood with a hole bored through the center to guide the spear and having elastic attached to the cylinder. The elastic is looped through a spear holder fitting and each end is attached to the cylinder. The elastic is stretched directly back by pulling on the spear holder fitting and is fired by releasing the spear holder fitting. The Hawaiian sling is also non-triggering and power of the spear is directly proportional to power of the rearward draw such that most tension is applied when the spear is in its aiming or ready position and is therefore difficult to hold while aiming.
Disadvantages inherent in the previous types of existing spear fishing devices described above are clear in that the speed of the projectile is dependent upon the strength of the user. Logically, the stronger the user, the more potential energy will be stored in the elastomeric material and the more kinetic energy that will be imparted to the projectile. For those sporting enthusiasts who enjoy the challenge of the hunt without the aid of more modern weapons, the traditional and existing spear fishing devices described above are difficult to use. Unless the sportsman is extremely strong, the projectile will not acquire a speed sufficient for hunting fish.
As in the development of a compound bow, a number of improvements may be made to the spear sling construction which utilize the enhanced force obtained through a simple application of physics. When cable is connected with the use of cams or eccentric pulleys, greater forces are more easily stored within the elastomeric material while reducing draw tension at an aiming position. Thus, with less strength, the user may easily hold a projectile at an aiming position and obtain a projectile velocity of a higher magnitude. As applied to a spear sling, such an improvement has clear advantages. The sportsman is able to enjoy the use of a spear sling without the disadvantages of the more basic designs.